Validamycin Inhibits the Reproductive Capacity of Spodoptera frugiperda (Lepidoptera: Noctuidae) by Suppressing the Activity of Trehalase

<i>Spodoptera frugiperda</i> (J. E. Smith, 1797), an omnivorous crop pest worldwide, reproduces prolifically. Validamycin, a competitive natural inhibitor of trehalase, is regarded as an effective and safe insecticide. Pupae were injected with a validamycin gradient (0.5-10 µg/µL) to block trehalase; enzyme activity and the Vitellogenin gene (<i>Vg</i>)/its receptor gene (<i>VgR</i>) expression (rpL10 reference) were subsequently quantified to determine the compound's impact on <i>S. frugiperda</i> ontogeny and fecundity. Validamycin directly inhibited pupal membrane-bound trehalase, sharply lowering glycogen. Both pupal and adult mortality rose with dose, yielding marked abnormalities versus the Control Check (CK) group. At 0.5 μg/μL validamycin, eggs blackened and clumped in the lateral oviduct, blocking release; treated females produced far fewer eggs by day 4, exhibited ovarian atrophy, shorter lifespan, and low hatchability. The expression levels of <i>Vg</i> and <i>VgR</i> in the ovaries of the fall armyworm were consistent with the changes in the ovarian developmental phenotype. Validamycin significantly inhibited the activity of trehalase in <i>S. frugiperda</i>, severely hindering their normal eclosion and lowering the potential reproductive capacity of <i>S. frugiperda</i>. Simultaneously, it directly affects ovarian development and the lifespan of female moths. The results provide data to support the development of new methods for controlling <i>S. frugiperda</i>.